Carcinomas associated with herpes viruses, or suspected of such an association, are obtained at surgery and propagated in cell culture. Using various methods, the attempt is made to develop permanent lines of carcinoma cells, free from fibroblasts or other contaminating cell types. Such lines are to be used in demonstrating a cell association with herpesviruses, through methods designed to elicit appearance of virus- or virus-associated antigens, or through detection of viral DNA.